In that aspect of dentistry which relates to tooth restoration, it is often required that an accurate dental model be made in a dental stone material of the affected tooth or teeth and the surrounding tissue areas. Many and various methods are known in the industry for providing such a model. In most such methods, paraphernalia including dowels, parting plates, sleeves, and the like, are positioned in the dental negative mould prior to the casting of any dental stone thereinto. The selected paraphernalia is traditionally fixed in the impression by one of several methods, as by luting the paraphernalia onto the inner wall of the impression with wax; or, a cross-member, suitably a paper clip, bobby pin, or match stick, is luted transversely across inner walls of the impression, i.e., from the buccal or labial wall to the palatal area, and then luting the dowel, sleeve, or dowel and parting plate assembly perpendicularly to the cross-member; or, the impression may be attached to a flask member of a complicated flask and superstructure arrangement wherein lugs provided on the flask member engage mating counterparts on the superstructure.
Regardless of the method used, a slurry of dental stone is then poured into the impression. If the flask/superstructure device is employed, the superstructure will be lowered into the slurry while the slurry is still soft.
The prior art methods and/or apparatus above-described, while generally satisfactory, suffer deficiencies and weaknesses substantially overcome by the present invention. For example, after carefully removing the separable or removable section or portion, i.e., the tooth die or dies, from the model, it was difficult to keep the dies in their original alignment. Repeated removals and insertions of the dies from and into the model further contributed to the poor alignment.
Also, if a dowel or mounting pin is employed in order to facilitate handling the tooth die as well as its repositioning back into the model or base stone, it was often-times difficult to accurately position a dowel relative to the negative impression of the tooth to be worked on. It is essential that a dowel be maintained in a substantially vertical position in the center of the impression of the tooth for proper removal of the tooth die. If a jig is used to hold the dowel, the vertical and lateral adjustment of the jig was difficult to manage.
Even where dowels are not required, as taught, for example, in U.S. Pat. No. 4,056,585, issued to the present applicant, protrusions or extensions on the outer surfaces of the die former are needed to assure the non-removability of the die former from the mould. Eye extensions, for passage therethrough of supporting pins which are pressed into the soft impression material for positioning the die former, are also required.
The present invention provides a jig which permits paraphernalia to be simply and precisely positioned within a negative dental mould or impression and requiring no dowels, parting plates, protrusions or extensions.
More specifically, the present invention comprises a pair of straight pins which are inserted into the negative impression substantially parallel to the root and crown axis of the affected tooth. A die forming member is provided with a pair of opposed laterally extending slotted tabs which engage the pins to thus permit versatile movement and precise positioning of the die forming member.